[PATCH] D135894: [clang][RISCV] Set vscale_range attribute based on presence of "v" extension

Thu Oct 13 10:52:34 PDT 2022

reames added a comment.

In D135894#3856229 <https://reviews.llvm.org/D135894#3856229>, @craig.topper wrote:

> There's also this patch from @frasercrmck https://reviews.llvm.org/D107290

So there is; had not seen that.  Looking at it, that patch seems to roll several items together.  I'd strongly prefer if we worked incrementally here.  I think we do need to merge the frontend and backend handling here, but we can we work one step at a time?

Steps as I currently see them:
Step 1 - get basic support for "v", to unblock practical codegen 
Step 2 - expose the necessary constants for frontend use, and rephrase in terms of VLEN
Step 3 - figure out why getMinVLen on RISCVISAInfo is currently always returning 0, fix that
Step 4 - revisit question if whether the result replaces TTI callback (I don't think it does, but don't want to speculate too much now.)

I'm willing to commit my time through at least step 3, and possibly beyond.

Repository:
  rG LLVM Github Monorepo

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  https://reviews.llvm.org/D135894/new/

https://reviews.llvm.org/D135894